SQL语句技巧:按月统计数据

表结构如下:

qty date
----------------------------------------------
13 2005/01/17
15 2005/01/19
3 2005/01/25
105 2005/01/27
1 2005/01/31
352 2005/02/03
12 2005/02/04
255 2005/02/07
6 2005/02/18
1 2005/02/19
28 2005/02/21
1 2005/02/22
394 2005/02/23
359 2005/02/24
313 2005/02/25
325 2005/02/26
544 2005/02/27
68 2005/02/28
2 2005/03/01
求一個SQL寫法,將每個月的數量求和,
如:
qry date
137 2005/01
?? 2005/02
?? 2005/03

SQL语句如下:
select sum(qty), datename(year, date) as year, datename(month, date) as month
from table
group by year, month